unix: add IoctlGetEthtoolTsInfo

The function fetches ethtool timestamping and PHC association for a
network interface. Its primary usage is to query the mapping between
the interface and its corresponding PTP clock number in /dev/ptp𝑛.

unix/ioctl_linux.go

@@ -58,6 +58,21 @@ func IoctlGetEthtoolDrvinfo(fd int, ifname string) (*EthtoolDrvinfo, error) {
 	return &value, err
 }
 
+// IoctlGetEthtoolTsInfo fetches ethtool timestamping and PHC
+// association for the network device specified by ifname.
+func IoctlGetEthtoolTsInfo(fd int, ifname string) (*EthtoolTsInfo, error) {
+	ifr, err := NewIfreq(ifname)
+	if err != nil {
+		return nil, err
+	}
+
+	value := EthtoolTsInfo{Cmd: ETHTOOL_GET_TS_INFO}
+	ifrd := ifr.withData(unsafe.Pointer(&value))
+
+	err = ioctlIfreqData(fd, SIOCETHTOOL, &ifrd)
+	return &value, err
+}
+
 // IoctlGetWatchdogInfo fetches information about a watchdog device from the
 // Linux watchdog API. For more information, see:
 // https://www.kernel.org/doc/html/latest/watchdog/watchdog-api.html.

unix/linux/types.go

@@ -4090,6 +4090,8 @@ const SPEED_UNKNOWN = C.SPEED_UNKNOWN
 
 type EthtoolDrvinfo C.struct_ethtool_drvinfo
 
+type EthtoolTsInfo C.struct_ethtool_ts_info
+
 type (
 	HIDRawReportDescriptor C.struct_hidraw_report_descriptor
 	HIDRawDevInfo          C.struct_hidraw_devinfo

unix/syscall_linux_test.go

@@ -68,6 +68,44 @@ func TestIoctlGetEthtoolDrvinfo(t *testing.T) {
 	}
 }
 
+func TestIoctlGetEthtoolTsInfo(t *testing.T) {
+	if runtime.GOOS == "android" {
+		t.Skip("ethtool driver info is not available on android, skipping test")
+	}
+
+	s, err := unix.Socket(unix.AF_INET, unix.SOCK_STREAM, 0)
+	if err != nil {
+		t.Fatalf("failed to open socket: %v", err)
+	}
+	defer unix.Close(s)
+
+	ifis, err := net.Interfaces()
+	if err != nil {
+		t.Fatalf("failed to get network interfaces: %v", err)
+	}
+
+	// Print the interface name and associated PHC information for each
+	// network interface supported by ethtool.
+	for _, ifi := range ifis {
+		tsi, err := unix.IoctlGetEthtoolTsInfo(s, ifi.Name)
+		if err != nil {
+			if err == unix.EOPNOTSUPP {
+				continue
+			}
+
+			if err == unix.EBUSY {
+				// See https://go.dev/issues/67350
+				t.Logf("%s: ethtool driver busy, possible kernel bug", ifi.Name)
+				continue
+			}
+
+			t.Fatalf("failed to get ethtool PHC info for %q: %v", ifi.Name, err)
+		}
+
+		t.Logf("%s: ptp%d", ifi.Name, tsi.Phc_index)
+	}
+}
+
 func TestIoctlGetInt(t *testing.T) {
 	f, err := os.Open("/dev/random")
 	if err != nil {

unix/ztypes_linux.go

@@ -4110,6 +4110,16 @@ type EthtoolDrvinfo struct {
 	Regdump_len  uint32
 }
 
+type EthtoolTsInfo struct {
+	Cmd             uint32
+	So_timestamping uint32
+	Phc_index       int32
+	Tx_types        uint32
+	Tx_reserved     [3]uint32
+	Rx_filters      uint32
+	Rx_reserved     [3]uint32
+}
+
 type (
 	HIDRawReportDescriptor struct {
 		Size  uint32